December 18, 2009
Mollified about Mercury (or Calm about Catfish)
Mercury in high doses is known to be toxic. So if you were thinking about breaking your glass thermometer and drinking the contents on a lark, I beg you to reconsider. This has raised concern about possible harm from eating seafood since many species of seafood are known to contain trace amounts of mercury. Much hand-wringing has ensued. Should we shun salmon? Avoid albacore?
The most recent issue of The Medical Letter, a publication I frequently cite, summarizes the scientific literature and attempts to clarify the issue.
Mercury exposure during pregnancy has been associated with problems with neurological development in the developing babies, though the results of studies of the effects of seafood intake during pregnancy have been mixed. Still, because neurodevelopment appears to be the biggest effect of mercury toxicity, concern has focused on pregnant and breastfeeding women and small children. The FDA (see link below) has recommended that pregnant and breastfeeding women limit their intake of seafood high in mercury.
In non-pregnant adults, no harm has been shown from mercury exposure from seafood. One possible reason is that the omega-3 polyunsaturated fatty acids (PUFAs) in fish oil have a beneficial protective effect that could outweigh any harm from the mercury in fish.
The authors of the article conclude:
Public health agencies have recommended limiting the intake of seafood with a substantial mercury content during pregnancy. Since the typical US seafood diet has a healthy ratio of omega-3 PUFAs to methylmercury and PCBs, the net effect of eating fish in the US is likely to be a protective one.
This is reassuring. I’m going to celebrate with a jar of herring.
The Medical Letter article: Mercury in Fish (by subscription only)
FDA advisory for Women Who Might Become Pregnant, Women Who are Pregnant, Nursing Mothers and Young Children: What You Need to Know About Mercury in Fish and Shellfish
Important legal mumbo jumbo: